class Solution {
public:
    int coinChange(vector<int>& coins, int amount) {
        // 完全背包刚好凑成amount
        const int n = coins.size(), INF = 0x3f3f3f3f;
        vector<int> dp(amount + 1, INF);
        dp[0] = 0;
        for(int i = 1; i <= n; ++i)
        {
            for(int j = coins[i - 1]; j <= amount; ++j)
            {
                dp[j] = min(dp[j], dp[j - coins[i - 1]] + 1);
            }
        }
        return dp[amount] >= INF ? -1 : dp[amount];
    }
};

/*class Solution {
public:
    int coinChange(vector<int>& coins, int amount) {
        // 完全背包刚好凑成amount
        const int n = coins.size(), INF = 0x3f3f3f3f;
        vector<vector<int>> dp(n + 1, vector<int>(amount + 1, INF)); // i结尾金额为j的最少个数
        dp[0][0] = 0;
        for(int i = 1; i <= n; ++i)
        {
            for(int j = 0; j <= amount; ++j)
            {
                dp[i][j] = dp[i - 1][j];
                if(j >= coins[i - 1])
                    dp[i][j] = min(dp[i][j], dp[i][j - coins[i - 1]] + 1);
            }
        }
        return dp[n][amount] >= INF ? -1 : dp[n][amount];
    }
};*/